Fig 1.
Profile photographs of pale (A-C) and dark species (D-F) (see text) of Myrmecocystus (subfamily Formicinae) examined in this study: (A) M. christineae (CASENT0923358), (B) M. navajo (CASENT0923356), (C) M. mexicanus-02 (CASENT0923355), (D) M. yuma (CASENT0923359), (E) M. kennedyi (CASENT0923362), and (F) M. mendax-03 (ASUSIBR00001132). Note the relatively larger eyes of pale compared to dark species. Species are arranged by size pairs–A&D, B&E, and C&F (see text). Photographs by Michele Esposito from www.antweb.org.
Fig 2.
Profile photographs of pale (A) and dark species (B-D) (see text) of Aphaenogaster (subfamily Myrmicinae) examined in this study: (A) A. megommata (CASENT0923367), (B) A. boulderensis (CASENT0005722), (C) A. occidentalis (CASENT0005725), and (D) A. patruelis (CASENT0923366). Note the relatively larger eyes of pale compared to dark species. Photographs by Michele Esposito from www.antweb.org.
Fig 3.
Profile photographs of pale (A) and dark species (B–C) (see text) of Temnothorax (subfamily Myrmicinae) examined in this study: (A) T. sp. BCA-5 (CASENT0118165), (B) T. neomexicanus (CASENT0923368), and (C) T. tricarinatus (CASENT0102845). Note the relatively larger eyes of pale compared to dark species. Photographs by Michele Esposito from www.antweb.org.
Fig 4.
Profile photographs of pale (A–B) and dark species (C–J) (see text) of Veromessor (subfamily Myrmicinae) examined in this study: (A) V. lariversi (CASENT0923345), (B) V. RAJ-pseu (CASENT0923346), (C) V. andrei (CASENT0923137), (D) V. chamberlini (CASENT0005730), (E) V. chicoensis (CASENT0923347), (F) V. julianus (CASENT0104946), (G) V. lobognathus (CASENT0923126), (H) V. pergandei (CASENT0923124, (I) V. smithi (MCZ-ENT00671466), and (J) V. stoddardi (CASENT0922825). Note the relatively larger eyes of pale compared to dark species. Photographs by Wade Lee, April Nobile, and Michele Esposito from www.antweb.org.
Table 1.
Brightness values, foraging time, and the four morphological traits measured for ant species examined in this study.
Brightness values are given as mean ± 1 SE (number of workers) (see text). Morphological measures are given as mean (± 1 SE) (also see Figs 5 & 7–9); for the three eye traits, values on the first line are raw data, values on second line are estimated marginal mean values using mesosoma length as a covariate in a multivariate analysis-of-covariance. Species are listed alphabetically by subfamily, genus, and species within each genus. Taxonomy follows Bolton [59]; species followed by a number are undescribed or in the process of revision [see 45]. Pale species in normal font; dark species in bold font (see text).
Table 2.
Association between color and activity period based on data in Table 1.
Pale species have a brightness (B) value > 65 and dark species have a B value < 60 as measured in Adobe Photoshop (see text).
Table 3.
Results for the homogeneity of variance-covariance and regression slopes assumptions in the MANCOVA.
The MANCOVA for each genus was run twice; the first run tested homogeneity of variance-covariance and homogeneity of regression slopes assumptions, and the second run was for results of the model. For the Levene’s test, the first column gives the P value for the assumptions run, the second gives the P value for the results run. Values for these three lines are eye area, facet number, and facet diameter, respectively. For Temnothorax, the first line is for all three variables, the second line is the model after deleting eye area (see text); values in the second line for the Levene’s test are for facet number and facet diameter, respectively.
Fig 5.
Eye area (mm2) (A), facet number (B), and mean facet diameter (D) (μm) (C) for species of Myrmecocystus (subfamily Formicinae: tribe Lasiini). Three species are pale (open symbols, normal font, and blue lines: M. christineae, M. navajo, M. mexicanus-02), and three species are dark (filled symbols, bold font, red lines: M. yuma, M. kennedyi, M. mendax-03) (see text). For each species, number of workers examined and number of colonies they were derived from is given in parentheses. Significant differences (P < 0.05) among species are denoted after each species name by the letters a–c: a > b > c; the three sets of letters for each species correspond to panels A, B, and C, respectively. Groupings are based on univariate F tests within MANCOVA using the estimated marginal means followed by pairwise comparisons using a least significant differences test (see text).
Fig 6.
Anterior ocellus diameter for species of Myrmecocystus (subfamily Formicinae: Tribe Lasiini).
Six species are pale (open or red symbols and normal font: M. christineae, M. ewarti, M. navajo, M. testaceus, M. mexicanus-01, M. mexicanus-02), and three species are dark (filled symbols and bold font: M. yuma, M. kennedyi, M. mendax-03) (see text). For each species, number of workers examined and number of colonies they were derived from is given in parentheses. Significant differences (P < 0.05) among species are denoted after each species name by the letters a–f: a > b > c > d > e > f; the three sets of letters for each species correspond to panels A, B, and C, respectively. Groupings are based on univariate F tests within ANCOVA followed by pairwise comparisons of the estimated marginal means using a least significant differences test (see text).
Fig 7.
Eye area (mm2) (A), facet number (B), and mean facet diameter (D) (μm) (C) for species of Aphaenogaster (subfamily Myrmicinae: tribe Stenammini). Aphaenogaster megommata is pale (open symbols and regular font), while A. boulderensis, A. occidentalis, and A. patruelis are dark (filled symbols and bold font) (see text). For each species, number of workers examined and number of colonies they were derived from is given in parentheses. Significant differences (P < 0.05) among species are denoted after each species name by the letters a–c: a > b > c; the three sets of letters for each species correspond to panels A, B, and C, respectively. Groupings are based on univariate F tests within MANCOVA using the estimated marginal means followed by pairwise comparisons using a least significant differences test (see text).
Fig 8.
Eye area (mm2) (A), facet number (B), and mean facet diameter (D) (μm) (C) for species of Temnothorax (subfamily Myrmicinae: tribe Crematogastrini). Temnothorax sp. BCA-5 is pale (open symbols and regular font), while T. neomexicanus and T. triacarinatus are dark (filled symbols and bold font) (see text). For each species, number of workers examined and number of colonies they were derived from is given in parentheses. Significant differences (P < 0.05) among species are denoted after each species name by the letters a–c: a > b > c; the three sets of letters for each species correspond to panels A, B, and C, respectively. Groupings for facet number and facet diameter are based on univariate F tests within MANCOVA using the estimated marginal means followed by pairwise comparisons using a least significant differences test (see text); groupings for eye area are based on a one-way ANOVA (see text).
Fig 9.
Eye area (mm2) (A), facet number (B), and mean facet diameter (D) (μm) (C) for species of Veromessor (subfamily Myrmicinae: tribe Stenammini). Veromessor lariversi and V. RAJ-pseu are pale (open symbols and regular font), while the other eight species are dark (filled symbols and bold font) (see text). For each species, number of workers examined and number of colonies they derived from is given in parentheses. Significant differences (P < 0.01) among species are denoted after each species name by the letters a–g: a > b > c > d > e > f > g; the three sets of letters for each species correspond to panels A, B, and C, respectively. Groupings are based on univariate F tests within MANCOVA using the estimated marginal means followed by pairwise comparisons using a least significant differences test (see text).
Fig 10.
Interommatidial angle (Δϕ) for one pale (open circles and regular font) and one dark (filled circles and bold font) (see text) species in each of four ant genera: (A) Myrmecocystus, (B) Aphaenogaster, (C) Temnothorax, and (D) Veromessor. All plots have the same x-axis and y-axis scaling in order to visualize differences between light and dark species across genera. Mean Δϕ (in degrees) is given after each species name with an asterisk denoting the species with a significant larger Δϕ based on a t-test (P < 0.05). The significant interaction of genus × activity period is shown by larger Δϕ’s for pale species of Myrmecocystus and Veromessor, whereas Δϕ was larger for dark species of Aphaenogaster and Temnothorax. Sample size is n = 5 for each species.
Fig 11.
Eye parameter (ρ) for one pale (open circles and regular font) and one dark (filled circles and bold font) (see text) species in each of four ant genera: (A) Myrmecocystus, (B) Aphaenogaster, (C) Temnothorax, and (D) Veromessor. All plots have the same x-axis and y-axis scaling in order to visualize differences between light and dark species across genera. Mean p is given after each species name with an asterisk denoting the species with a significant larger p based on a t-test (P < 0.05). The significant interaction of genus × activity period is shown by larger differences between light-colored and dark-colored species of Aphaenogaster compared to those in the other three genera. Sample size is n = 5 for each species.
Fig 12.
Anterior-posterior visual field span (in degrees) for one pale (open circles and regular font) and one dark (filled circles and bold font) (see text) species in each of four ant genera: (A) Myrmecocystus, (B) Aphaenogaster, (C) Temnothorax, and (D) Veromessor. All plots have the same x-axis and y-axis scaling in order to visualize differences between pale and dark species across genera. Mean visual field span (in degrees) is given after each species name with an asterisk denoting the species with a significant larger visual field based on a t-test (P < 0.05); the double asterisk denotes that the t-test was not significant, but that the visual field was significantly larger when including mesosoma length as a covariate. The significant interaction of genus × activity period is shown by larger differences between pale and dark species of Aphaenogaster compared to those in the other three genera. Sample size is n = 5 for each species.
Fig 13.
Regional variation in facet diameter for one pale (open circles and regular font) and one dark (filled circles and bold font) (see text) species in each of two ant genera: (A) Myrmecocystus and (B) Veromessor. Significant differences within each species are denoted by the letters a–c: a > b > c for pale species; d–f: d > e > f for dark species. Groupings for each species are based on a repeated-measures ANOVA followed by a least significant differences test. Sample size is given after each species name.
Table 4.
Repeated measures ANOVA results for regional variation in facet diameter for one pale (normal font) and one dark species (bold font) (see text) of Myrmecocystus and Veromessor (n = 12 per species for Myrmecocystus; n = 14 per species for Veromessor).
Table 5.
Additional pale ant species (see text) with enlarged eyes based on photographs examined on Antweb (www.antweb.org).
Species are listed alphabetically by subfamily, genus, species group, species, and subspecies. High resolution photographs of each species can be viewed by going to https://www.antweb.org/advSearch.do, then placing the genus and species name in the advanced search box. Brightness values are given as mean (n) (see text). Relative eye size was calculated as eye area/mesosoma length.